Modern internal combustion engines are equipped with sophisticated systems to monitor and control various aspects of engine performance during ongoing operation, to meet operator demands for performance, including torque and fuel economy, and to satisfy government regulations related to emissions, safety, and fuel economy. Such systems include sensing devices and actuators connected to one or more control modules which execute computer programs to monitor and control engine operation during ongoing operation.
Exhaust pressure is an important parameter used by engine system designers. By way of illustration of a need for an accurate determination of exhaust pressure, emissions requirements have led to implementation of exhaust gas recirculation (EGR) systems combined with aftertreatment systems to reduce engine emissions. Control of exhaust gas recirculation requires an accurate determination of EGR mass flow. Such methods include calculating EGR flow from a gas flow equation through an orifice, and, determining a difference between charge air mass flow and fresh air mass flow. Both calculations use engine exhaust pressure as one of the input variables. Some engine manufacturers have implemented an exhaust pressure sensor to determine exhaust pressure.
There is a need to estimate exhaust pressure for an internal combustion engine, to accurately determine exhaust pressure without incurring additional costs associated with additional of sensing devices.